Anybody with a stir plate and an O2 meter able to tell me...

[Hermit]

How long does it take to raise boiled water, reportedly oxygen deprived, up to the the theoretical maximum of 8ppm?

 

[ajdelange]

Depends on many things like how vigorously you are stirring, how finely divided the bubbles are on exiting the stone, the flow rate through the stone, the volume of the water. I've found that with pure O2, a sintered stainless stone and a flow rate of about 0.5 LPM that 3 - 5 gal of wort can be brought to about 20 mg/L in about 3 min.

 

[Hermit]

Thanks. Reading your answer makes me realize my head cold made me blow the initial question though. (That and I still haven't figured out people can't read my mind) I'm thinking just a plain stir plate with stir bar. According to popular beer practices lure boiling drives the oxygen out. My canned starter wort should be pretty devoid of oxygen.

Chris White states in his book that yeast will consume all oxygen in wort in about an hour. I'd have to go back and see if he is referring to a 5 gallon batch. A starter is going to be a massive over pitch in that regard. So, would I/WE be better off letting the stir plate run a bit before we pitch the yeast? If so how long? Once it goes anaerobic and the krausen forms it seems that would stop further oxygenation.

 

[RmikeVT]

One of the advantages to using a stir plate is that you do not have to oxygenate the starter wort because the constant stirring will introduce all the oxygen you need, assuming you don't have an airlock. I simply sanitize a square of foil and loosely crimp around top of starter.